Enhance curriculum catalog functionality: Update CONTRIBUTING.md to reflect changes in curriculum structure, including the introduction of curriculumCoverage for frameworks. Modify frontend components to support a new comparison view for Mathematics, allowing users to compare curricula. Update catalog data to include "Common Core" and improve curriculum filtering logic. Enhance styles for better visual representation of curriculum badges and Mermaid diagrams. Adjust TypeScript types to accommodate new features and ensure backward compatibility with legacy curriculum data.

CONTRIBUTING.md

@@ -28,12 +28,12 @@ Thank you for helping grow free, open textbooks.
 ## How the catalog fits together
 
 ```text
-data/{subject}-curriculum.json  → catalog list + map (status, curriculums, graph.edges)
+data/{subject}-curriculum.json  → catalog list + map (status, curriculumCoverage, graph.edges)
 content/{subject}/{slug}/       → everything for the live page (one folder)
   _index.md, core.html, supplement.html, assets/, widgets/, chapter.scss
 ```
 
-- **Catalog** (`/catalog/`) — list and map (`?view=tree`). Curriculum names (DSE, IB, …) appear only in the catalog — not inside chapter prose ([spec.md](spec.md)).
+- **Catalog** (`/catalog/`) — list, map (`?view=tree`), and for Mathematics a Compare doc (`?view=compare`, HTML partial `themes/openfreebooks/templates/partials/math-curricula-compare.html`). Curriculum names (DSE, IB, …) appear only in the catalog — not inside chapter prose ([spec.md](spec.md)).
 - Every chapter needs a **`description`** in curriculum JSON (map clamps to three lines).
 - **`bun run sync:chapters`** (also run automatically by `bun run build:js`) merges `core.html` + `supplement.html` into `_index.md` for Zola. Edit the HTML files, not the merged body in `_index.md`.
 
@@ -61,11 +61,17 @@ content/{subject}/{slug}/       → everything for the live page (one folder)
   "title": "Human-readable title",
   "description": "One or two sentences for the catalog list and map card.",
   "status": "planned",
-  "curriculums": ["DSE"],
+  "curriculumCoverage": {
+    "DSE": "core",
+    "IGCSE": "core",
+    "IB": "related"
+  },
   "tier": "non-foundation"
 }
 ```
 
+Each framework maps to `core`, `extension`, or `related` (Compare matrix). Use `extension` for elective / M2-style topics; `related` when the topic supports but is not a named unit.
+
 3. Use **kebab-case** slugs. No `content/` folder needed for planned chapters.
 
 ---
@@ -74,7 +80,7 @@ content/{subject}/{slug}/       → everything for the live page (one folder)
 
 ### 1. Catalog entry
 
-In `data/{subject}-curriculum.json`, set `"status": "live"` and include `description`, `curriculums`, and optional `tier`.
+In `data/{subject}-curriculum.json`, set `"status": "live"` and include `description`, `curriculumCoverage`, and optional `tier`.
 
 ### 2. Chapter folder
 
@@ -187,7 +193,7 @@ Omit `banner` for subjects that should stay unchanged (e.g. roadmap-only placeho
 ## Add a curriculum label
 
 1. Add the label to `curriculums` in `data/catalog.json`.
-2. Tag chapters in their `curriculums` arrays.
+2. Add roles per chapter in `curriculumCoverage` (and update Compare if needed).
 3. Add badge style in `themes/openfreebooks/sass/_catalog.scss` and mapping in `frontend/src/lib/catalog-badge.ts`.
 
 ---